TOEFL Reading: ETS-TOEFL阅读机经 - 5XTP63CI0E4Z8041L$

In paragraph 2, why does the author describe how ice-skaters use their arms to increase their speed of rotation? A. To help describe the armlike structures on a spiraling nebula B. To help explain why a nebula rotates faster when it contracts C. To show why spinning ice-skaters are not pulled down by gravity D. To show how the motion of a nebula differs from that of an ice-skater